On Wed, Dec 9, 2020 at 9:51 AM Linus Walleij [off-list ref] wrote:

On Tue, Dec 8, 2020 at 3:07 PM Enrico Weigelt, metux IT consult [off-list ref] wrote:

What we need to understand is if your new usecase is an outlier
so it is simplest modeled by a "mock" irq_chip or we have to design
something new altogether like notifications on changes. I suspect
irq_chip would be best because all drivers using GPIOs for interrupts
are expecting interrupts, and it would be an enormous task to
change them all and really annoying to create a new mechanism
on the side.

I would expect the platform abstraction to actually be close enough
to a chained irqchip that it actually works: the notification should
come in via vring_interrupt(), which is a normal interrupt handler
that calls vq->vq.callback(), calling generic_handle_irq() (and
possibly chained_irq_enter()/chained_irq_exit() around it) like the
other gpio drivers do should just work here I think, and if it did
not, then I would expect this to be just a bug in the driver rather
than something missing in the gpio framework.

       Arnd